Sixt Car Rental - Barcelona El Prat Airport - BCN - Spain

We arrived at Barcelona and went to the Sixt desk to pick up the 4x4 we had reserved and paid for. Upon checking in at the desk, we were advised that there were no 4x4 vehicles left. Not a great start as we were heading off to a ski resort. The whole reason we had booked one. We were given a free upgrade to a brand new BMW and given snow chains for free, which was better than nothing should the snow have been awful. I provided my credit card as requested and my husband handed over his driving licence. We were asked if we wanted any additional drivers to which we said no as it was going to cost more money. We returned the vehicle with no issues after a week. When we arrived home, we had been charged £55. I contacted Sixt to enquire what the extra charge was for. I was advised that it was for the additional driver. I explained how we specifically said we did not want any additional drivers and how I didn't produce my driving licence because of this. Sixt explained that because I gave them my credit card, I was the main driver and my husband had been added as an additional driver! I tried to tell them that we had said we didn't want an additional driver, this hadn't been explained at the desk and that the form my husband had signed was in Spanish. So there was no way of us knowing about this extra charge. Sixt have been particularly unhelpful in their replies and will not provide us with any compensation for something that we believe is their fault. We will never use them again for car hire as it appears they are beyond incompetent.